The predictions of the witches.
When Macbeth meets the witches he is taken aback by their predictions because they reflect what he is thinking. Also the use of “fair and foul” by both Macbeth and the witches adds to this.
When Duncan sees Macbeth’s castle he states that the castle has a pleasant air, a foreshadowing of what is to happen to him.
The witches’ predictions about Banquo’s and his descendants also foreshadow what their fate will be. Also their references to no man born of woman (Macduff), and till Birnam Wood come to Dunsinane are further examples.